Communications equipment, computers, work stations, automated test and production equipment, military targeting systems, home stereo systems, televisions, and other electronic devices as well as electrical loads using integrated circuits, solid state components, switching power supplies, semiconductor networks and the like, are increasingly characterized by small electrical contacts and miniature components which are very vulnerable to interference or damage due to interference from electrical disturbances carried by power line conductors connected thereto. Unpredictable variations in power line conductor voltage changes the operating range and can severely damage or destroy such devices. These devices and related process problems are very expensive to repair or to replace and therefore require cost-effective protection from transients and surges associated with the power.
Accordingly, the electrical art has included several devices for protecting sensitive communications and power installations, as well as other types of a-c loads, from damaging power surges and transients.
These devices are generally added on to a power distribution system. Examples of such "add on" devices are disclosed in patents such as U.S. Pat. No. 4,675,772 (the disclosure of which is incorporated herein by reference) and U.S. Pat. No. 4,835,650 (the disclosure of which is incorporated herein by reference). These devices are added to an already existing wiring system by being connected to a main breaker panel which connects building wiring to utility power wiring, or by being connected to a subpanel located at or near a point of use, such as at a floor or other such building area.
A circuit breaker panel assembly that is intended to protect communications and power installations, as well as other types of a-c loads, from damaging power surges and transients is disclosed in co-pending patent application Ser. No. 07/655,853, now U.S. Pat. No. 5,191,502, filed on Feb. 15, 1991 and assigned to the assignee of the present invention, and the disclosure of which is incorporated herein by reference. This panel assembly includes a voltage surge and transient protection circuit that is integral therewith, and overcomes the drawbacks noted above.
However, any circuit breaker panel assembly, even the assembly disclosed in the incorporated patent application, should be monitored, if not continuously, then on a systematic periodic basis. The inventor has found many problems that are attributed to equipment really are caused by problems in the circuit breaker panel assembly. Some of the problems are caused by overloading the panel or by improper wiring being connected to the panel after the panel has beer installed in order to add equipment to the building, or because the panel assembly was not modified when non-linear loads were added, or the like. The inventor has also found that errors in wiring associated with the added equipment have created problems in the panel assemblies. Monitoring of such panels might alert the proper personnel about such problems at an early stage, or at least before such panel assembly related problems create equipment problems, or problems that are attributed to the equipment connected to the panel assembly. Furthermore, even in the normal course of operation, as user may wish to monitor to ensure that surge suppression and filtering are operating properly.
However, the inventor has found that at the present time, circuit breaker panels are monitored, if at all, only on an erratic basis with a possibility of long lapses between checks and are often monitored by personnel who are not fully versed in power technology and the theories, principles and problems associated therewith, and are not skilled in data analysis techniques. This erratic monitoring is even more erratic if there are numerous panel assemblies in a single building. In fact, some panel assemblies in remote or inaccessible locations of a building may never be monitored or checked after initial installation thereof.
Therefore, all circuit breaker panel assemblies, even that panel assembly disclosed in the incorporated patent application having an integral protector network, should be checked periodically to be sure that the panel assembly is functioning according to design criteria, and is providing results that are within design ranges. Some reasons for this need were alluded to above, and specific examples of the need are presented below.
For example, because light bulb and motor-type loads have neutral currents which are phasors that tend to sum to zero, many three-phase panels use a neutral bus which is sized for the same or smaller amperage as the phase supply connectors. This permits the neutral to be smaller and less expensive. However, computer loads (i.e., switching power supplies) are non-linear. They do not sum to zero on the neutral, but actually can sum to 3.sup.1/2 larger than the phase currents. Still further, many panels have small lugs which necessitate the use of small wiring. Such small wiring may be a source of overheating, noise or voltage drops. The neutral bus in many of these panels is also subject to overheating. Overheating may impair the proper operation of the panel, and may even damage the bus. Therefore, a panel assembly that was designed for linear loads may be prone to problems if non-linear loads are connected thereto. Operation that endangers a panel assembly elements, such as a neutral bus, should be identified and corrected as soon as possible. Such identification of problems, especially with neutral bus overheating, is best carried out during a monitoring and testing operation of the circuit breaker panel assembly.
Still further, while a panel assembly may have been installed when a certain load was connected thereto, due to building modifications or the like, that same panel assembly may, at a later time, be required to carry more, or different, loads. This situation may occur when a panel assembly is installed in a multi-story building during construction of that building, and then not modified as the building is rented out to those who add loads to the panel assembly, or as more and more equipment is connected to the same panel assembly. The panel assembly may work well for some loading, but have various problems when that loading is exceeded or altered.
Therefore, there is a need for a means and a method for enabling a skilled technician or a skilled data analyst to monitor a circuit breaker panel assembly on a systematic basis, or even on a continuous basis. Of course such monitoring must be efficient and economical.
There is still further need for such circuit breaker panel assembly monitoring to be carried out to monitor specific parameters of the panel assembly as well as the performance of various components of the panel assembly, including any voltage surge and transient protection equipment associated with the panel assembly.